Images of a truck believed to be the suspect's vehicle, taken at the Santa Rosa Transit Mall, were included in a CHP news release Friday. The images were discovered during an investigation Friday into a report of a Feb. 11 incident where a water bottle was thrown at a Santa Rosa CityBus, Sloat said. There were no damages or injuries reported from that incident, he said.

Two of the six confirmed incidents involved school buses, including one that occurred last week but which was first called in to authorities Friday. The bus driver reported suffering minor injuries when the bottle shattered the windshield and sprayed her with broken glass.

The injury elevates the investigation to a felony case. There were no children on either bus at the time of the attacks.

Outside of the Transit Mall incident, the confirmed reports occurred between 11 a.m. and 3 p.m. on roads between Santa Rosa and Sebastopol.

Sloat said the CHP has assigned an investigator to the case and is "giving extra attention" to those areas. However, some of the new reports indicate attacks may have occurred farther east in Santa Rosa. Sloat said anyone with information should call his office at 588-1400.

"We obviously don't want people following the suspect, but we are hoping that someone will see the driver or get a license plate or other detail," he said. "Short of that, it's going to be hard to pin this on anybody."

Both the damaged school buses are operated by the West County Transportation Agency. Thursday's incident occurred at about 1 p.m. as the driver, Emily Keeran, 28, travelled eastbound on Occidental Road near Piezzi Road. The bottle hit and broke the glass of the driver's side mirror.

"I saw a big flash of white and silver," said Keeran, who was not hurt and managed to pull over to the side of the road. "It really shook me up. When I was driving back to the yard, I kept seeing white pickups and thinking ,'Please don't hit me, please don't hit me.'"

Keeran was on her way to pick up special education students at Mark West Elementary school.

"I've been driving a bus for eight years and I've never seen anything like this," she said. "Thank goodness my kids weren't on the bus."

Mike Rea, executive director of the WCTA, which operates buses for 16 school districts in Sonoma County, said the first bus incident was thought to be an accident. Because there were no children were on the bus, there was no legal requirement to report it to the CHP, he said.

"When our second bus was hit, we thought it was too much of a coincidence," he said.

Rea said the damages to the buses amounted to about $350 and included replacing a side mirror and windshield. While he said they were taking the incidents seriously, there wasn't much more they could do to take further precautions.

Three reports Wednesday involved vehicles being hit, including one incident where a bottle broke through a windshield, leaving a large hole. The driver pulled to the side and wasn't injured, according to reports.

Wednesday's cases occurred within minutes, in the late morning. The bottles were thrown at vehicles on Highway 12 near Irwin Lane, on Llano Road and on Highway 12 near Merced Avenue.